The invention relates to a wiper drive for a rear window wiper of a motor vehicle.
A wiper drive is an encapsulated drive unit for the oscillating pivoting movement of a wiper arm about an axis of rotation in order to guide a wiper blade connected to the wiper arm between two turning positions over a windshield and consequently to remove impurities or wet spots from said windshield. The wiper drive can be used in particular on a rear window wiper of a motor vehicle. Here, the wiper shaft is usually protected by means of a protective cap against penetrating moisture and foreign bodies. The protective cap is connected by means of a radial press connection to a cylindrical formation of a housing of the wiper drive, with the wiper shaft extending through the formation. The relatively hard protective cap is in turn surrounded by a soft rubber bush in the region of a lead-through through a vehicle body or through the windshield of the motor vehicle. The wiper drive is connected at elastically mounted suspension points to the body of the motor vehicle in order to provide insulation with respect to structure-borne noise and vibrations.
During the wiping operation, the wiper drive moves relative to the body of the motor vehicle owing to the wiper forces which occur. As a result of this movement, owing to a so-called pumping action, axial forces are exerted on the protective cap which attempt to free the protective cap from its press connection with the housing of the wiper drive and pull it off in the upward direction. Further axial forces can occur when an impulse acts in the axial direction on the wiper drive or the wiper arm, for example when banging closed a tailgate of the motor vehicle on which the wiper drive is fastened.